Apraxia of speech (AOS) is a disorder affecting the motor planning of speech and can be associated with neurodegenerative diseases. It can occur in isolation or in the presence of a language disorder whereby patients have problems with grammar and spoken language, known as non-fluent aphasia (NFA). It is unclear how longitudinal structural and functional changes in the brain are related to the heterogeneous clinical features of the disorder. Characterizing progression in neurodegenerative AOS will be critical for patient prognosis and for further defining these disorders for future research and clinical trials. The objectives of the studies outlined in this application are to determine the relationship between structural and functional changes in the brain and progression of speech and language, neurological and neuropsychological features in patients with AOS. To accomplish our aims we will utilize a well characterized cohort of neurodegenerative AOS subjects that were evaluated at the Mayo Clinic, Rochester MN, and have undergone standardized speech and language, neurological and neuropsychological evaluations, a magnetic resonance imaging (MRI) scan and a [18-F]-fluoro-deoxy-glucose (FDG) positron emission tomography (PET) scan. In this study, we will perform two additional serial assessments of each patient, with the first performed 2.5 years after their original assessment, and the second performed one year later. Each assessment will include identical speech and language, neurological and neuropsychological evaluations and an MRI and FDG-PET scan. Therefore, three serial assessments will be available for analysis in this study. We will assess the rate of brain tissue loss, and examine which specific brain regions and white matter tracts change over time. Changes in brain metabolism and functional connectivity will also be assessed. We will then investigate associations between these imaging measures and different aspects of clinical decline, as well as develop imaging-based models that predict clinical outcomes, such as worsening of AOS and the development of NFA in patients with isolated AOS. Importantly, since we would have followed patients for a number of years, we anticipate that some subjects will die during the study and hence we will be able to perform brain autopsies to determine what disease(s) are present in the brain and develop neuroimaging models to predict brain pathology. The application focuses on neuroimaging and will be led by a Principal Investigator with 10 years experience in neuroimaging research involving these neurodegenerative disorders. She will also have support from a team of world renowned scientists including dementia, movement disorders and speech pathology specialists, a nuclear medicine scientist, neuropsychologists, and biostatisticians. The long term goal of our research is to develop neuroimaging biomarkers in neurodegenerative AOS and provide results that will help improve predictions about the course of clinical decline.